Massachusetts’ New Bedford Harbor is one of the country’s most polluted waterways. For 40 years, nearby factories and shipping vessels have been dumping pollution into it, and it's so grimy that there's been a ban on fishing in much of the area since 1979. So why is one species of fish thriving there?
According to the Environmental Protection Agency, two manufacturing plants near the harbor spent much of mid-20th century improperly dumping polychlorinated biphenyls (coolant fluids used in motor production) and heavy metals into the harbor, contaminating sediment as far as six miles away. The EPA has been working on cleaning up the harbor since 1982, but it remains a highly toxic area.
Like Blinky the three-eyed fish in The Simpsons, fish in the harbor have rapidly evolved to cope with the toxic waters. In a new paper published in BMC Evolutionary Biology, researchers from Woods Hole Oceanographic Institution say that the 3-inch-long Atlantic killifish (Fundulus heteroclitus) is dominating the harbor. Not only are they dominating the harbor, but they burrow into the toxic sediment for most of winter and spend most of their time in summer there, unlike other fish.
EPA guidelines for the fishing ban in New Bedford Harbor. Image: EPA
A genetic change in the fish has modified a receptor protein called AHR2. In normal fish, AHR2 regulates cellular functions—PCBs stimulate it, eventually causing toxicity and death. In killifish, the receptor isn’t fully turned off, but it is significantly dulled, making PCB ultimately less toxic to them. Only killifish living in the harbor seem to show this modified receptor—killifish living elsewhere have the normal receptor.
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